Workflow in WSS 3.0 Randomly Stops Working until Re-Saved

Question

Using SharePoint designer, I created a custom workflow associated with a library that sends an email out to specific people when a document is checked in and marked as ready for review. We're running WSS 3.0. The workflow works great. Until it doesn't work
at all. It randomly stops all aspects of the workflow - no logs are generated, no emails are sent - nothing happens at all until I open the workflow in SharePoint designer and re-save it. I don't change anything, just resave it. Then it works again until it
randomly stops.

The build version is 12.0.0.6565.

It
is a problem with a single workflow, not all workflows.

No
problems with permissions and no db restores. Opening the WF in designer and re-saving it is all that's needed to get it working again.

1. I know it's not an email sending issue. The first step in the WF is to log a message and that doesn't even happen. In addition, I don't have the "stopped" status. Finally, in desparation, I tried this anyway and it made no difference.
:-)

2. I don't know when it breaks. Can you give me a idea of what to look for in the ULS log? Or am I just looking for something "off".

Microsoft is conducting an online survey to understand your opinion of the Technet Web site. If you choose to participate, the online survey will be presented to you when you leave the Technet Web site.